Suppression of Rayleigh-Taylor type fluctuations by velocity shear

Experimental investigation of the curvature induced Rayleigh-Taylor (R-T) instability in the presence of a sheared electric field is reported in a low-β toroidal plasma device, BETA (Basic Experiments in Toroidal Assembly). Coherent low frequency fluctuations are excited at 200 gauss. The R-T instability arises from an unfavourable curvature in the magnetic field (simulating the effective gravity) with density gradient (▿n) antiparallel to it and the sheared electric field is inbuilt in the device. Results show that the R-T instability driven fluctuations are suppressed where the E(r) x B shear is above a critical value. This critical value of shear is found to be consistent with the theoretical predictions.